In general, supplemental restraint systems perform a number of functions including acceleration sensing, signal processing and analysis, and deployment of one or more restraint devices such as frontal or side air bags or seat belt pretensioners in response to a sensed crash event. Typically, the acceleration signal is monitored to detect a potential crash event, and then filtered or integrated over the course of the crash event to produce a velocity change or .DELTA.V signal. If the .DELTA.V signal exceeds a threshold, the crash event is determined to be sufficiently severe to warrant deployment of restraints. The threshold is typically time-dependent, and is calibrated based on data logged for different types of crash events, as well as data logged during rough road driving.
A problem with the above-described approach is that it is often difficult to distinguish between deployment events such as high speed crashes and non-deployment events such as curb impacts, rough road impacts and animal impacts, since the acceleration signal associated with the non-deployment events can exceed the acceleration associated with a deployment event, particularly in the initial portion of the crash event.